JP2016038927A - Data storage device, data recording method of data storage device, data reproduction method of data storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a data storage device and the like, which can read recording data of a plurality of tracks with a single reproduction head simultaneously and decode the data with a high data transfer rate proportional to the number of the tracks.SOLUTION: The data storage device comprises: a recording head recording data on each of a plurality of tracks; a recording medium; a reproduction head having a width substantially equal to the sum of widths of the plurality of recording tracks; and a data processing part (reproduction data processing part) simultaneously reading data of the plurality of tracks from the reproduction head and processing an obtained signal. The record medium has a structure in which recording bit magnetization of the adjacent tracks for one bit is arranged with a phase shifted along a head movement direction by only a length that is shorter than a recording magnetization length for one bit equal to the shortest magnetization transition interval. The data processing part separates and decodes magnetization information data of each recording track and performs signal processing for achieving a high data transfer rate, based on a signal to which a magnetization signal of tracks read at a time by the reproduction head is added.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a data storage device, a data recording method for the data storage device, and a data reproducing method for the data storage device, and more particularly, to a data storage device used for recording and reproducing digital data such as a hard disk device and a magnetic tape device. It relates to data recording and playback methods.

  Up to now, data storage devices have been developed mainly by improving the surface recording density, which is the number of recording bits per unit area on the recording medium. The surface recording density is the product of the linear density in the traveling direction of the head recording medium and the track density which is the density per unit length of the recording track in the cross track direction. To date, both linear density and track density have increased approximately equally and have made balanced progress, but in recent years it has become technically more difficult to improve linear density and the recording track width The rate of improvement in track density is narrowing.

On the other hand, the hard disk drive can provide superior performance because the higher the data transfer speed for reading and writing, the less time is required for data transfer.
However, the improvement in the surface density depending on the track density can ensure the recording capacity required for the hard disk device, but the data transfer speed is insufficient. This is not only a hard disk device but also a magnetic tape device.

By the way, with the recent increase in file size and data amount, there is a strong demand for an improvement in data transfer speed in a data storage device. Due to the enormous amount of information recorded, the time required to access information will become longer unless the transfer rate is improved, and high-speed recording and playback that can send and receive large amounts of data in a short time, that is, faster data transfer It is essential.
Since the data transfer speed in a data storage device is given by the product of the linear density and the relative speed between head media, the linear density is not only an increase in recording capacity, but also an important performance factor that determines the speed of data transfer. is there. In particular, in a magnetic disk apparatus, the relative speed between head media is proportional to the radius of the recording track and the disk rotation speed, but the track diameter is determined by the size of the disk, and the power consumption and disk rotation stability are also affected by the disk rotation speed. There is an upper limit due to securing, etc., and it cannot be increased without darkness.
However, this improvement in the linear density cannot always be easily improved due to the resolution limitation at the time of recording, the limit of the flying height between the head disks, and the spatial resolution of the reproducing head.
For this reason, in recent years, there is a tendency to increase the surface recording density by increasing the track density which is easier to improve. In particular, shingled magnetic recording, which uses a wide track width recording head to create a narrow track width recording by moving the recording head at narrower intervals than the track width during recording. Is a typical method for obtaining a high track density (see Non-Patent Document 1, for example).

Roger Wood, Mason Williams, Aleksandar Kavcic, and Jim Miles, “The Feasibility of Magnetic Recording at 10 Terabits Per Square Inch on Conventional Media”, IEEE TRANSACTIONS ON MAGNETICS, FEBRUARY 2009, VOL.45, NO2, p.917-923 Sato, Muraoka, Nakamura, “Multitrack Batch Playback Method Using Multilevel Partial Response”, Journal of Japan Society of Applied Magnetics, supplement S2, 1995, p.92-95 Kikawada, Honda, Ouchi, “High-track density recording method using orthogonal codes for adjacent tracks”, IEICE Technical Report, 1994, MR94-104 Y. Maruko, K. Miura, H. Muraoka, “Study of simultaneous readback of two shingled tracks,“ ICAUMS2012 / 36th Conference on Magnetics in Japan, 4pA-4, p.248 Yamamoto, Miura, Aoi, Muraoka, “Linearity of adjacent track superposition waveform in single recording”, Journal of Japan Society of Applied Magnetics, 2011, Vol.35, No.5, p.409-413

  However, the technique described in Non-Patent Document 1 is a technique for recording at a high surface recording density, and is not a technique for reading data recorded at a high surface recording density at a high speed to increase the data transfer speed.

  The inventor of the present application has considered that if a plurality of tracks can be reproduced simultaneously, the data transfer rate can be increased in proportion to the number of tracks.

However, in the prior art, each track is recorded and reproduced independently, and only one track is read out simultaneously. Therefore, in order to read out a plurality of tracks at the same time, a plurality of reproducing heads capable of reproducing simultaneously are required. However, the normal track width is extremely narrow, such as several tens of nanometers, and it is not easy to arrange read heads close to each other with high accuracy.
If a single playback head can be used to simultaneously reproduce and decode the information of multiple tracks, the track width of the playback head can be roughly the sum of the track widths recorded on multiple disks. It is not necessary to form a narrow track width, and there is an advantage in manufacturing a reproducing head.

However, if, for example, simply using a wide reproducing head to simultaneously reproduce data corresponding to the magnetizations recorded on a plurality of tracks at the same time, the data transfer rate is increased. Data (information) recorded on the track is added at the time of reading. This means that strong crosstalk noise between tracks, also called ITI (Inter Track Interference), is mixed, so the signal quality of the original target track is greatly impaired, and multiple tracks at each time are left as they are. Cannot be read and separated and decoded.
For example, the data (signal) based on the recording magnetization of each track is +1 or −1 which is two directions upward or downward on the disk surface in the perpendicular magnetic recording, and the data based on the recording magnetization of the two tracks is simultaneously obtained by the wide reproducing head. The addition signal obtained by reading out is one of four types: + 1 + 1 = + 2, + 1−1 = 0, −1 + 1 = 0, and −1-1 = −2. For this reason, when the addition signal obtained by reading the recording magnetization of two tracks by the wide reproducing head is 0 (zero), it cannot be distinguished which track is +1 and which is −1, and decoding is impossible.

Up to now, since two tracks are simultaneously reproduced and decoded by one reproducing head, the +1 and -1 magnetizations are alternately finely formed with an extremely high linear density, which cannot be read with the reproducing head resolution, and equivalent. A proposal has been made to introduce a typical zero magnetization level (see Non-Patent Document 2, for example).
If three different magnetization levels can be used per track by introducing an equivalent zero magnetization, + 1 + 1 = 2, + 1 + 0 = + 1, 0 + 0 = 0, -1 + 0 = -1, and −1−1 = −2 Since the combination of the signal levels after the addition becomes possible, multi-value recording by selecting four ways from here enables the combination of four or more kinds of recording magnetizations in the simultaneous reproduction of the two-track single reproducing head, Data can be recorded.
However, it is difficult and widely realized to form equivalent zero magnetization with higher linear density recording exceeding the reproducing head resolution for equivalent zero magnetization in the state where the linear density is increased to the limit in normal recording. It did not come. There is also a problem that noise from zero magnetization is large and the SN ratio at the time of decoding deteriorates. That is, in order to realize zero magnetization, it is necessary to lower the original linear density to a lower linear density on the basis of the high linear density of alternating recording for zero magnetization, and there is no advantage in increasing the transfer rate.

  Also, if recording magnetization is formed using orthogonal codes, information on non-target tracks can be erased by signal processing at the time of reading. A proposal for separating and decoding data (for example, see Non-Patent Document 3) is known. However, this method has the disadvantage that the number of bit magnetizations on the disk requires 4 bits (4 symbols in the code recorded on the disk) in order to record 1 bit of input user data, resulting in poor encoding efficiency. . This means that the transfer rate is reduced to 25% per track, and this is a practical disadvantage that it is reduced to half even when two tracks are parallel.

  As described above, in the conventional magnetic recording method, data of a plurality of tracks are added and read by a single head, and the data of each track is separated and decoded from the added signal at a linear density equivalent to that of single track recording / reproduction, thereby transferring the transfer rate. Recording / reproduction increased in proportion to the number of tracks could not be performed.

  This invention makes it an example of a subject to cope with such a problem. That is, simultaneously reading data recorded on two or more tracks with a single head to obtain a high data transfer rate and decoding the data with high coding efficiency, a recording medium such as a disk The purpose is to realize a high data transfer speed without increasing the relative speed of the reproducing head.

  When recording and reproducing a plurality of tracks, the phase of the magnetization transition position of the adjacent track with respect to the magnetization area for 1 bit of each of the two tracks is shifted by half the length of 1 bit along the head moving direction. Signal quality when recording and reading simultaneously from two tracks by one wide reproducing head (for example, see Non-Patent Document 4 and Non-Patent Document 5) has been studied, and multiple tracks are read by a single reproducing head. Therefore, it is confirmed that the addability (linearity) of the signal is not almost lost. According to this, when decoding a multiple-track simultaneous reproduction signal, a decoding method based on the linearity is effective.

  In order to achieve such an object, the data storage device according to the present invention temporarily records the recording data in each of the plurality of tracks to be collectively reproduced, in a semiconductor buffer memory, etc. Means for appropriately allocating and recording data, comprising: a reproducing head arranged over two or more adjacent tracks of the recording medium; and two or more tracks of the recording medium A data processing unit for processing an addition signal obtained by simultaneously reading out data in the recording area by the reproducing head, and the recording medium has a recording magnetization for one bit of an adjacent track in the head moving direction. And having a structure in which the phase is shifted by a length smaller than the length of the recording area of 1 bit along the data processing unit, Addition signal (reproduction signal) obtained by simultaneously reading a plurality of tracks by a reproducing head having a track width substantially equal to the sum of the plurality of track widths for collectively reproducing the recording magnetization data of two or more tracks of the recording medium And a processing unit for performing a process of decoding the recording track magnetization data.

  In the data storage method of the data storage device of the present invention, binary data to be recorded on the recording medium of the data storage device is temporarily stored in a semiconductor buffer memory or the like, and then a plurality of tracks are recorded based on a predetermined method. And writing to the recording area of each track by the recording head. Storing input data once in a high-speed semiconductor buffer memory also has the effect of improving the equivalent data transfer speed during recording.

  In the data storage method of the data storage device of the present invention, the addition obtained by the data processing unit simultaneously reading the recording magnetization data of two or more tracks of the recording medium of the data storage device by the playback head. A process of decoding the recording magnetization data from the signal is performed.

The data storage apparatus according to the present invention reads out data recorded on two or more tracks simultaneously with a single reproducing head without increasing the relative speed between a recording medium such as a disk and the head. It can be decoded at a high data transfer rate.
Further, according to the present invention, it is possible to provide a data recording method for the data storage device and a data reproduction method for the data storage device.

The functional block diagram which shows an example of the data storage apparatus which concerns on this invention. 1 is a conceptual diagram showing an example of a spatial arrangement of a plurality of batch playback recording tracks and a wide playback head on a recording medium of a data storage device according to a first embodiment of the present invention. The conceptual diagram for demonstrating the principle decoding method in the data storage apparatus which concerns on 1st Example of this invention. The figure which shows an example of the data storage apparatus which reads 3 tracks by a single head. FIG. 9 is a conceptual diagram for explaining an operation of a data storage device according to a second embodiment of the present invention, (a) is a diagram showing an example of a head and a track, and (b) is a diagram showing an example of a conversion table. The conceptual diagram which shows an example of track arrangement | positioning and a clock point in the data storage apparatus concerning 3rd Example of this invention. The figure which shows an example of the reproduction | regeneration pulse after passing through the equalizer by the partial response system which concerns on 3rd Example of this invention. The figure for demonstrating an example of the operation | movement about the state transition regarding the decoding by the partial response and the most favorable decoding (PRML) system of the data storage apparatus which concerns on 3rd Example of this invention. The partial response (121) channel state transition diagram in the two-track batch reproduction. Partial response (121) Trellis diagram when channel state transition is applied to 2-track parallel recording. The figure which shows an example which reproduced the magnetization signal of 2 tracks collectively with the single wide track reproducing head with respect to the signal at the time of reproduction | regeneration of a continuous bit, and decoded by the partial response and maximum likelihood decoding system.

  A data storage device according to an embodiment of the present invention includes a recording medium such as a disk on which data is recorded, a recording data processing unit that records data on each of a plurality of tracks, a recording head that writes information on the recording medium, A reproducing head having a track width substantially equal to the sum of the widths of adjacent tracks of a recording medium to be collectively reproduced, and a head obtained by simultaneously reading the recording magnetization of the plurality of tracks of the recording medium simultaneously by the reproducing head And a data processing unit that performs a process of decoding data based on the reproduction signal.

  Specifically, the data storage device temporarily stores input recording data in a semiconductor buffer memory or the like at the time of recording, and appropriately divides and records the data on a plurality of adjacent tracks on the recording medium according to a decoding method. By reproducing a plurality of adjacent tracks in parallel at the same time by a reproducing head, an equivalently high data transfer rate is realized. Specifically, the data storage device collects the input data temporarily at the time of recording, the means for dividing and recording the data into a plurality of tracks by an appropriate method, and the data of the plurality of tracks by a reproducing head having a wide track width. Reproducing means for reading simultaneously and a data processing unit for decoding data from reproduced signals (addition signals) read in a lump.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Specifically, for example, a data storage device used for recording / reproducing digital data on a magnetic recording medium such as a hard disk device or a magnetic tape device will be described. Also, a data recording method for the data storage device, a data reproduction method for the data storage device, and the like will be described.

  The embodiment of the present invention includes the contents shown in the drawings, but is not limited to this. In the following description of each drawing, parts that are common to the parts that have already been described are assigned the same reference numerals, and duplicate descriptions are partially omitted.

FIG. 1 is a functional block diagram showing an example of a data storage apparatus 10 according to the present invention.
The data storage device 10 includes a head 1 such as a recording head 1w (1) and a reproducing head 1r (1), a recording medium 2, a recording data processing unit 11, a buffer memory 12 (storage unit), and an encoder / error correction code adding unit. 13, a head selector circuit 14, a spindle motor 18, a drive circuit 19, a control circuit 20, a reproduction signal amplification unit 21, an equalizer 22, a reproduction data processing unit 23, a decoder / error correction unit 25, and the like. The recording head 1w is also referred to as a recording head 1, and the reproducing head 1r is also referred to as a reproducing head 1.

For example, the recording data processing unit 11 records binary data input from a computer 8 (PC) or the like on a recording medium 2 in a buffer memory 12 composed of a semiconductor memory or the like once on a plurality of tracks. After storing data to be recorded, a process of appropriately distributing the data to a plurality of tracks based on a predetermined method is performed to generate data to be recorded on each track. The generated data is sequentially recorded as magnetization information on the recording medium for each track according to the disk rotation.
Specifically, the recording data processing unit 11 converts the input binary data by a recording method corresponding to each embodiment, and generates data to be recorded on each track.

  The encoder / error correction code adding unit 13 encodes the data output from the recording data processing unit 11 such as run length restriction necessary for magnetic recording and the like, and performs parity for error correction processing. Predetermined encoding processing such as bit addition is performed.

  The head selector circuit 14 selects a plurality of recording heads and reproducing heads, and outputs the signal output from the encoder / error correction code adding unit 13 to the recording head 1w (1). A recording current corresponding to the recording code is applied to the recording head 1w (1), but the recording current application circuit is omitted here. The head selector circuit 14 selects an appropriate reproducing head when reading data from the disk, and outputs the reproduction signal to the reproduction signal amplifying unit 21.

  The spindle motor 18 rotates the recording medium 2 such as a disk, for example. The head actuator moves the head to a specific track position based on the drive signal from the drive circuit 19, and then causes the reproducing head to follow the target track with high accuracy.

  The drive circuit 19 outputs a drive signal to the head actuator and the spindle motor 18 under the control of the control circuit 20.

  The control circuit 20 as a control unit controls each component of the data storage device 10, and the control circuit 20 controls the recording data processing unit 11, the reproduction data processing unit 23, and the like.

  The reproduction signal amplifier 21 is an amplifier such as an automatic gain control circuit (AGC) or a variable gain amplifier (VGA), and amplifies and outputs the signal output from the reproduction head 1r (1).

  The equalizer 22 includes a filter, an equalizer, and the like, and removes unnecessary components such as noise from the signal from the reproduction signal amplification unit 21 and outputs the result. Further, the equalizer 22 has a role of equalizing the head reproduction signal into an analog signal waveform having a predetermined waveform in a partial response method described later.

  The reproduction data processing unit 23 uses the addition signal obtained by simultaneous batch reading of the magnetization of two or more tracks of the recording medium by the reproduction head 1r (1) and a specific method for specifying the data in the recording area. Then, a process of decoding the magnetization data of a plurality of recording tracks is performed. The detailed operation of the reproduction data processing unit 23 will be described later.

  The decoder / error correction unit 25 has a function reverse to that of the encoder / error correction code adding unit 13 and converts the magnetic recording code into normal binary information such as NRZ. The decoder / error correction unit 25 performs a predetermined error correction process on the data from the reproduction data processing unit 23 and outputs the data.

  Data from the decoder / error correction unit 25 is output to a computer 9 (PC) or the like.

  For example, the control circuit 20 controls the recording data processing unit 11, the buffer memory 12, the encoder / error correction code adding unit 13, the head selector circuit 14, the drive circuit 19, and the like, and the recording head 1 w (1) controls the recording medium. Record data in 2.

  Further, for example, the control circuit 20 controls the head selector circuit 14, the reproduction signal amplification unit 21, the equalizer 22, the reproduction data processing unit 23, the decoder / error correction unit 25, and the like, thereby reproducing the reproduction head 1 r (1). Thus, the data is read from the recording medium 2 and reproduced to decode the data.

<First embodiment (recursive decoding)>
FIG. 2 is a conceptual diagram showing an example of the spatial arrangement of a plurality of batch reproduction recording tracks and a wide reproduction head on the recording medium of the data storage apparatus 10 according to the first embodiment of the present invention.

  The recording medium 2 may be a magnetic disk or the like, or a magnetic tape. The recording medium 2 may be a vertical recording system or a horizontal magnetic recording system. In this embodiment, a perpendicular recording method is adopted. In this case, binary data can be recorded in association with bits by magnetizing the recording area vertically upward or downward with respect to the magnetic film (magnetic material).

In the recording medium 2, a plurality of tracks 1 and 2 are recorded as magnetization according to data. Specifically, in FIG. ₃ , track 1 is recorded magnetization bits (magnetization bits) of A ₁ , A ₃ , A _{5 in} time series, and track 2 is recorded magnetization bits of A ₀ , A ₂ , A ₄ , A _6. It is shown. The magnetization length of each magnetization in the head running direction (the horizontal direction in the figure) is the bit length, and is equal to the distance between the magnetization transitions for each bit magnetization. Therefore, the linear density corresponds to the number of recorded magnetizations entering per unit length. The recording track width corresponds to the recording magnetization width in the depth direction of FIG. In the figure, the track width of the reproducing head 1 is approximately equal to twice the recording track width.

In the present invention, it is assumed that the magnetization bits are out of phase in adjacent recording tracks. For example, when the magnetization bits A ₁ and A ₂ or A ₂ and A ₃ of adjacent recording tracks are compared, the center positions of the 1-bit recording magnetizations are staggered. When viewed as a signal, the phase differs by a half bit length. The magnetization transition that is the boundary between A ₀ and A ₁ corresponds to the bit center of the magnetization bit A ₁ of the adjacent track. That is, each of the recording magnetization bits 3 has a structure in which the phase is shifted by a length smaller than the bit length of the recording magnetization bit 3 for one bit along the head moving direction.

The reproducing head 1 is formed to have a wide width. Specifically, the reproducing head 1 has a track width substantially equal to the width of two or more adjacent tracks on the recording medium 2. In the present embodiment, the reproducing head 1 is arranged over two or more tracks of the recording medium 2 and is configured to be able to simultaneously read data of recording magnetization bits of two or more tracks. ing. Specifically, in the example shown in FIG. 2, the head 1 moves in the right direction in the figure, or the recording medium 2 moves in the left direction in the figure, so that the head 1 has two adjacent tracks (track 1, track 2). ) At the same time and outputs an addition signal (reproduction signal).
As shown by X ₁ , X ₂ , X ₃ ,... In FIG. 2, the data read point detects the output signal of the read head 1 twice at the midpoint between the front half and the back half of each 1-bit magnetization. Clock position that can be. For example, for A ₁ , the output is read twice at times X ₁ and X ₂ . Specifically, the addition signal X ₁ is the addition value of the data of A ₀ and A ₁ , the addition signal X ₂ is the addition value of the data of A ₁ and A ₂ , and the addition signal X ₃ is the data of the data of A ₂ and A ₃ . The addition value, the addition signal X ₄ is the addition value of the data of A ₃ and A ₄ , the addition signal X ₅ is the addition value of the data of A ₄ and A ₅ , and the addition signal X ₆ is the addition value of the data of A ₅ and A ₆ ....

  The data processing unit decodes the data by processing the addition signal obtained by simultaneously reading the recording magnetization bit data of two or more tracks of the recording medium 2 by the reproducing head 1.

FIG. 3 is a conceptual diagram for explaining a principle decoding method in the data storage apparatus according to the first embodiment of the present invention.
Next, the first embodiment will be described with reference to FIG. 3 and the above-described drawings. In the first embodiment, 1-bit magnetization information is detected by sampling twice, and decoding is performed recursively using 1-bit previous information. Specifically, in this embodiment, the data processing unit is obtained from the head 1 when the reproducing head 1 moves by at least one bit of the recording magnetization length in the reproducing head moving direction with respect to the recording medium 2. A processing unit that recursively decodes the head reproduction signal obtained by the second sampling using the head reproduction signal preceding the two head reproduction signals.

At the time of recording, a series of binary input data a _(k) (k indicates a bit number in time order) are alternately distributed and recorded on a plurality of tracks. Here, since the direction of the reproducing magnetic flux detected by the reproducing head changes depending on whether the recording magnetization of the magnetic recording is upward or downward on the disk surface, the binary element is assumed to be composed of +1 and −1. The subscript represents the time of each data element.

The input data is divided into N = 2, that is, divided into two tracks and recorded in parallel. Specifically, data b _{1 (k)} and b _{2 (k)} for recording on the recording medium 2 are generated corresponding to each track. At this time, as shown in FIG. 3, the first bit data b _{2 (1)} of the track 2 has the initial value of the binary input data a set to −1, and the input data a ₍₂₎ = − which is the next bit. 1 is recorded as data b _{1 (1)} of track 1.
The next input data a ₍₃₎ = + 1 is recorded as data b _{2 (2)} , that is, the second bit of track 2. Similarly, a ₍₄₎ = −1 is recorded as the second bit of track 1 in b1 ₍₂₎ .
After that, input data is allocated to track 1 and track 2 alternately, and track 1 is continuously recorded as a ₍₂₎ , a ₍₄₎ ,... Recording is performed for each track, a ₍₁₎ , a ₍₃₎ ,.

  In the reproduction process, a signal obtained by adding both tracks is reproduced by the reproducing head 1 having a wide track width for reading both recording magnetization bits of the track 1 and the track 2 at a time.

  For example, in the comparative example (conventional example), +1 is recorded on track 1 and -1 is recorded on track 2, and -1 is recorded on track 1 and vice versa. The value of the addition signal is 0, and decoding is impossible.

  In the first embodiment of the present invention, oversampling is performed twice for each recording magnetization bit of each track. Therefore, the same data is continuously recorded in the same recording area (bit cell) in each track. Using this property, data can be obtained by subtracting a known bit from the addition signal.

For example, a case where the addition signal c _(k) and k = 2 will be described (a range surrounded by a dotted line in FIG. 3). In this case, since data is -1 in track 1 and data is +1 in track 2, 0 is output from head 1 as an addition signal.
It is known that the value of the data b _{1 (1)} of the same recording area (bit cell) is −1 at the time of decoding one clock before, that is, at the time of k = 1, going back one bit. Using this data recursively for decoding at the second clock with k = 2, the value of the data b _{1 (2)} of track 1 is −1 and the value of the addition signal from the reproducing head 1 is 0. Thus, by subtracting the bit magnetization −1 of track 1 from the added signal c ₍₂₎ = 0, it can be decoded that the value of the data b _{2 (2)} of track 2 is +1.

That is, in this embodiment, when the reproducing head 1 is moved by the recording magnetization length corresponding to a half bit length in the head moving direction with respect to the recording medium 2, the data processing unit 2 Based on the addition signal, the value of the addition signal of one track is set recursively equal to obtain the signal of the other track, so that the data recorded in the recording area is recursively decoded, so a simple configuration Thus, the data of two tracks can be decoded by estimating and subtracting crosstalk noise (inter-track interference).
Further, in this embodiment, since data in the recording areas of a plurality of tracks of the recording medium is decoded based on the addition signal obtained by reading the data from the single reproducing head 1 in parallel at the same time, the data of two tracks is obtained. The data is output simultaneously in parallel and has a double data rate.

  Here, two tracks are exemplified, but even when N tracks of three or more tracks are parallel, the phase difference of the recording magnetization bits of the adjacent tracks at the time of recording is set to 1 / N of the magnetization bit length and 1 bit at the time of reproduction. The data transfer rate can be increased N times by detecting the signal by N times oversampling. By performing a recursive operation using the fact that the 1-bit magnetization oversampled at the time of decoding is the same value, even with N tracks, only one unknown track magnetization can be obtained for each clock. Become.

FIG. 4 is a diagram showing an example of a data storage apparatus that reads out three tracks by a single head.
As shown in FIG. 4, the data storage device may be configured so that three tracks among a plurality of tracks recorded on the recording medium 2 are read by a single head.
In this case, the recording medium 2 has a structure in which recording areas for 1 bit of adjacent tracks are respectively shifted in phase by 1/3 of the length of the recording area for 1 bit along the head moving direction. .
Further, as in the first embodiment, the second embodiment (described later), and the third embodiment (described later), data is recorded on each track of the recording medium, and three tracks are simultaneously read by a single head. As a result, the data transfer speed becomes high.
Note that the expansion can be similarly performed in the case of four or more tracks.

<Second Embodiment (Decoding Using Precoder (Precoder))>
FIG. 5 is a conceptual diagram for explaining the operation of the data storage apparatus according to the second embodiment of the present invention. Specifically, FIG. 5A is a diagram illustrating an example of the head 1 and a track, and FIG. 5B is a diagram illustrating an example of a conversion table.

In the recursive decoding method of the first embodiment described above, the next bit is decoded using the decoded bit. If an error occurs, the next bit is also erroneously decoded. There is. For example, in FIG. 3, if b _{1 (1)} is mistaken for +1 due to noise mixing, the value to be subtracted from the addition signal 0 at the time of decoding of c ₍₂₎ is not correct -1, but is incorrect +1, and is decoded. b _{2 (2)} results in an error of -1. As a result, the error continues to propagate for the next b _{1 (3)} .

In order to improve this, in the second embodiment, when data is alternately recorded on a plurality of tracks, the data is encoded in advance by a precoder (pre-encoder), and the addition signal for each clock is decoded. Prior to recording, the data obtained by calculating the input data by an appropriate precoder so as to coincide with the power data is recorded on each track of the recording medium with the phase shifted as in the first embodiment.
Then, at the time of reading by the reproducing head, a process of decoding data based on the conversion signal from the addition signal from the reproducing head having a wide width from a plurality of tracks is performed.

  As an example, as shown in FIG. 5, when the bit magnetization of two tracks is +1 and the addition signal by the reproducing head is +2, both the two-track bit magnetization is −1 and the reproducing head output is −2. In this case, it is assumed that the decoded data is +1, and when the bit magnetization of one of the two tracks is +1 and the bit magnetization of the other track is −1, it is decoded as −1. Here, the conversion table is used for outputting output data in correspondence with the addition signal from the reproducing head.

  In the second embodiment, the recording data processing unit 11 distributes the binary data to be recorded on the recording medium 2 of the data storage device 10 to a plurality of tracks so as to match a predetermined conversion table. It is generated by a recording data processing unit using a precoder (pre-encoding), and magnetization information is written to each track by the recording head 1w (1).

  In the second embodiment, the reproduction data processing unit 23 includes a processing unit that performs a process of decoding data based on the addition signal obtained by the reproduction head and a conversion table for converting the addition signal into data.

Next, a specific description will be given.
As shown in FIG. 5A, when the initial value of track 2 is c ₍₁₎ = −1, the first input data a ₍₁₎ is −1. _{In (1)} , the sum signal from the reproducing head, which is the sum of c ₍₁₎ of track ₁ and b ₍₁₎ of track 2, should be 0, which is a value that is −1 from the conversion table. B ₍₁₎ is previously set to +1 by the precoder.
The next bit remains the same bit cell b ₍₂₎ = + 1 for track 1, and the bit magnetization of track 2 is c ₍₂₎ so that the reproduction head output obtained by adding track 2 to this becomes -1. May be set to -1.
Since the bit magnetization of track 2 is also a bit cell whose c ₍₃₎ = is −1 in the _third bit, b ₍₃₎ of track 1 is −1 in order for the decoded output to be +1.

  Thus, in the second embodiment, the reproduction data processing unit 23 decodes data for each clock based on the conversion table for obtaining decoded data from the added signal obtained by the head 1. Therefore, in the second embodiment, it is not necessary to recursively use the decoded data at the previous time, and decoding can be performed only with the addition signal of two tracks at a certain clock time, and thus there is an advantage that there is no error propagation.

<Third embodiment (partial response / maximum likelihood decoding)>
In the third embodiment, partial response / maximum likelihood decoding (PRML) is used in the data storage apparatus of the multitrack simultaneous reproduction system according to the present invention.

FIG. 6 is a conceptual diagram showing an example of track arrangement and clock points in the data storage apparatus according to the third embodiment of the present invention. At the time of recording, the input data is shifted by a half bit length in the same manner as in the first and second embodiments, and is alternately allocated to the adjacent tracks of the recording medium 2 for recording.
Typically, the encoder output bits may simply be assigned alternately to A ₀ , A ₁ , A ₂ , A ₃ ,. The clock point data detection at the time of reproduction is different from the first and second embodiments, r ₁ of the central position with respect to 1 bit magnetization, r _2, · · ·, r _i-1, r _i , r _{i + 1} , and the reproduction signal is sampled only once at the center for 1-bit magnetization. Here, since the recording magnetization bits are arranged alternately, when there is a clock point at the center of bit magnetization on one side, the bit magnetization of the other track corresponds to the magnetization transition position at the boundary.

  In the two-track parallel recording, the bit length of the recording magnetization bit with respect to the clock interval can be increased as compared with the conventional partial response recording method. For example, in 2-track parallel recording, the bit length of the recording magnetization of each track can be extended to two clock intervals for sampling a signal. This means that the recording magnetization bit length itself can be a long bit length that does not require an excessively high recording resolution while the clock interval for determining the transfer rate is set narrow.

  FIG. 7 is a diagram showing an example of a reproduction pulse after passing through an equalizer in the partial response system according to the third embodiment of the present invention. Here, as a partial response of perpendicular recording, an integral type PR (121) channel having a response of (1, 2, 1) to input 1 is shown, but the same applies to PR channels of other classes such as PR (1331). The effect of is obtained. This waveform is obtained by appropriately superimposing a sinc function or a pulse according to the sinc function as usual. In the figure, a sinc pulse having a peak amplitude of 2 at the center and a sinc pulse having a pair of peak amplitudes of 1 on the left and right are superimposed. It is. Also, this pulse can be realized by using an equalizer for the output waveform of the reproducing head, and no special means is required.

FIG. 8 is a diagram for explaining an example of the operation regarding the state transition related to the decoding by the partial response / maximum decoding (PRML) method of the data storage apparatus according to the third embodiment of the present invention. The partial response / maximum likelihood decoding method can be applied to simultaneous reproduction of a plurality of tracks as described below.
It is a figure explaining an example of the reproducing head output signal of the two-track parallel reproduction by the response of a partial response (121) channel divided into the response from track 1 and track 2. Since the channel is a 3-bit response of 121 to input 1, the playback response is determined by the next bit in a state where 2 bits are received.
A series of signals of white circles 0, 1, 2, 1, 0 at the left end of the figure is a response of the partial response (121) to the +1 magnetization bit of track 1, and the following white triangle mark indicates the magnetization of track 2 − Since it is a partial response (121) response to the magnetization of 1, it is 0, -1, -2, -1, 0. In the state of passing through + 1-1 and 2 bits, at the read point indicated by the white arrow, the response is + 1-2 = -1. Here, when 0, 1, 2, 1, 0 occurs as a response from the track 1 to the +1 magnetization as indicated by a white square, the signal of the reproducing head observed at the read point is -1 + 1 = 0. In this way, when a 0 signal is generated from the reproducing head in the state of + 1-1, it can be seen that the next magnetization bit is +1.
On the other hand, if the recording magnetization bit −1 appears twice in succession in track 1 and track 2 as another combination, if the recording magnetization bit in the next track 1 is +1, −1 + −2 + 1 = −2 Is observed as the reproducing head output. If the bit magnetization of the track 1 in the state of -1-1 is -1, the signal becomes -4. By obtaining this in all cases, it is possible to obtain the state transition diagram of the partial response (121) channel in the two-track batch reproduction of FIG.

  By doing so, it is possible to estimate the next state transition from the signal level of the next received reproduction waveform in the state at the time when the reproduction of a certain bit is completed. Since this state transition is associated with the decoded data as shown in FIG. 9, it can be decoded by following the combination.

  FIG. 10 is a trellis diagram when the state transition of the partial response (121) channel is applied to 2-track parallel recording. This figure is a rewrite of the state transition diagram with the horizontal axis as the time. Follow the path from left to right according to the state up to a certain time of 2 bits and the signal from the playback head at that time. Thus, the magnetization bit can be decoded. For example, the second “−1 + 1” from the top of the left state indicates that the value of the first bit of the preceding recording magnetization is “−1” and the value of the next succeeding bit magnetization is “+1”. Show. At this time, if the output of the reproducing head is +2, the “+1” magnetization bit is recorded continuously, and in the decoded state, the state changes to + 1 + 1 and moves to the bottom of the right state. become. That is, after the bit magnetization of −1 and +1 continues, if the read head output is +2, the next magnetization bit is +1, and next, +1 changes to the state twice in succession.

  In practice, the output of the playhead is not exactly +2, but has some noise errors. Using the difference between this error and the original signal (in this case +2) in the trellis diagram, it is possible to quantify the degree of certainty (likelihood) that the state transition in the trellis diagram has occurred. In the maximum likelihood decoding for multi-track batch reproduction, the most probable decoding sequence can be obtained by the same operation as the conventional maximum likelihood decoding. Therefore, the likelihood is calculated using this trellis diagram and Viterbi decoding is performed. The output sequence is obtained.

  FIG. 11 shows an example in which a 2-bit magnetized signal is collectively reproduced by a single wide track reproducing head based on the above method and decoded by a partial response / maximum likelihood decoding method with respect to a signal during continuous bit reproduction. FIG. In the figure, the vertical axis indicates the voltage of the addition signal detected by the head, and the horizontal axis indicates the time for each bit. Here, a 10-bit sequence of −4, −4, −2, 2, 2,... Is shown, but it can be correctly decoded even if noise is mixed in a longer data sequence. is there.

  Thus, in the partial response / maximum likelihood decoding of the third embodiment, even when a signal obtained by reading a plurality of tracks with a wide head includes noise and the SN ratio is reduced, the error rate is not deteriorated. Data can be decrypted.

  Although the partial response (121) channel is illustrated here, the present invention is not limited to this, and an optimal partial response channel can be used.

In the two-track simultaneous reproduction, the bit cell magnetization is shifted by a half bit length, so that an equivalently high data transfer rate can be obtained even if the bit length of the recording magnetization is increased. This corresponds to the fact that high-speed data transfer / reproduction that is proportional to the number of tracks to be reproduced at once is possible even when the recording / reproducing resolution of the recording / reproducing head or the magnetic disk is the same as the conventional one. On the other hand, the recording process requires high recording resolution of the recording head and the magnetic disk, and the linear density restrictions of recent magnetic disk devices that require extremely strict specifications for the resolution and flying height of the reproducing head during reproduction can be relaxed. Is an advantage.
Since the data speed is doubled using two tracks, the surface recording density itself does not change.

As described above, the data storage device 10 according to the embodiment of the present invention has a recording medium 2 that records data on each of a plurality of tracks and the width of two or more adjacent tracks on the recording medium 2. Data processing for processing a head reproduction signal obtained by simultaneously reading the reproduction data 1 of the reproduction head 1 having a width equal to or larger than the sum and the recording data of two or more tracks of the recording medium simultaneously by the reproduction head 1 (Reproduction data processing unit 23).
The recording medium 2 is arranged with the phase shifted by a length smaller than the recording magnetization length of 1 bit, which is equal to the shortest magnetization transition interval, along the moving direction of the recording magnetization bit of 1 bit of the adjacent track. It has a structure.
The data processing unit uses the appropriate means to record the recording magnetization bit data with respect to the addition signal obtained by simultaneously reading the data in the recording areas of two or more tracks of the recording medium by the reproducing head 1. A processing unit that performs a process of decoding the data.
Therefore, a data storage capable of simultaneously reading out data recorded on two or more tracks by a single reproducing head 1 to obtain a high data transfer rate and decoding the data with high accuracy. An apparatus 10 can be provided.
In addition, the data storage device 10 can realize a high data transfer speed without increasing the relative speed between a recording medium such as a disk and a reproducing head, for example.

  In other words, according to the present invention, even if the same head disk system as the conventional application example is used, an equivalently high data transfer speed and linear density can be realized, and thus high speed data transfer can be realized while keeping the relative speed of the head disk constant It can be done.

Further, the data processing unit (reproduction data processing unit 23) of the data storage device according to the embodiment of the present invention has at least one recording magnetization bit of the reproducing head 1 in the reproducing head moving direction with respect to the recording medium 2. By performing data sampling at least twice while moving by the length, the information obtained by decoding the preceding addition signal based on the continuous addition signal obtained by the reproducing head 1 continues to the sampling time. And a processing unit that recursively decodes the data recorded in the recording magnetization bit by using the generated reproducing head signal.
For this reason, the data recorded on each track is recursively based on the addition signal obtained by simultaneously reading out a plurality of tracks by the single wide track reproducing head 1 which has not been realized so far with a simple configuration. It is possible to provide a data storage device that can be decrypted.

In addition, the data processing unit (reproduction data processing unit 23) of the data storage device according to the embodiment of the present invention performs an operation on the recording data by the precoder in advance, so that the addition signal obtained by the reproduction head 1 at the clock point. On the other hand, it has a processing unit capable of decoding data for each bit based on a conversion table for converting into decoded data.
More specifically, binary data to be recorded on the recording medium is distributed to a plurality of tracks based on a conversion table defined in advance by a pre-encoder (precoder), and written to the recording area of each track by the head. Then, the reproduction data processing unit 23 performs a process of decoding the data based on the addition signal obtained by the head 1 and the conversion table for converting the addition signal into data as the specific information, so that the data can be easily obtained. Can be decrypted. In this case, data can be decoded without causing error propagation.

Further, the data storage device according to the embodiment of the present invention records and records the recording magnetization bits on a plurality of recording tracks on the recording medium so that the center of each bit is the magnetization transition point of the other track magnetization bits. A means for reading out the magnetization information by sampling at the center of the magnetization bit of each track is provided, and the data processing unit (reproduction data processing unit 23) adds the reproduction response by the reproduction head 1 to the recording areas of a plurality of tracks. An equalizer that equalizes the signal so as to be a partial response channel, and a processing unit that performs a process of appropriately decoding data by a maximum likelihood decoding method based on the signal from the equalizer.
Therefore, it is possible to provide a data storage device that can perform high-speed decoding at a data transfer rate proportional to the number of tracks from which data is simultaneously read by partial response / maximum likelihood decoding (PRML).

  Further, the data recording method of the data storage device according to the embodiment of the present invention distributes binary data to be recorded on the recording medium of the data storage device 10 to a plurality of tracks based on predetermined specific information, The reproducing head 1 performs processing for writing in the recording area of each track. Therefore, it is possible to record predetermined data in a data storage device that reads a plurality of tracks simultaneously by a single reproducing head by a simple process.

  In addition, a recording medium on which the data is recorded can be provided.

  In addition, the data reproducing method of the data storage device according to the embodiment of the present invention is obtained by simultaneously reading the data of two or more tracks of the recording medium of the data storage device by the reproducing head 1 by the data processing unit. Based on the reproduction signal and the means for specifying the data in the recording area, a process for decoding the data in the recording area is performed. Therefore, it is possible to provide a data reproduction method for a data storage device that can decrypt data by simple steps.

As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to these embodiments, and there are design changes and the like without departing from the gist of the present invention. Is included in the present invention.
Further, the embodiments described in the above drawings can be combined with each other as long as there is no particular contradiction or problem in the purpose and configuration.
Moreover, the description content of each figure can become independent embodiment, respectively, and embodiment of this invention is not limited to one embodiment which combined each figure.

In the above embodiment, data is recorded on a magnetic disk as a recording medium, and data is read from the magnetic disk. However, the present invention is not limited to this form. This patent is effective when there are a plurality of recording tracks adjacent to each other and when a reproduction signal in which an addability between the tracks is obtained when they are reproduced collectively.
For example, data may be recorded on a magnetic tape and data may be read from the magnetic tape.

1 ... Head (playback head, recording head),
1r: reproducing head,
1w: Recording head,
2 ... Recording medium,
3. Recording magnetization bit,
10: Data storage device,
11: Recording data processing unit (data processing unit)
12: Buffer memory (storage unit),
13 ... Encoder error correction code adding unit 14 ... Head selector circuit,
18 ... Spindle motor,
19 ... Drive circuit,
20 ... control circuit (control unit),
21. Reproduction signal amplification circuit,
22: Equivalent device,
23 ... Data processing unit for reproduction (data processing unit),
25: Decoder error correction unit.

Claims (6)

A data storage device,
A recording medium for recording data on each of a plurality of tracks;
A read head disposed over two or more adjacent tracks of the recording medium;
A data processing unit for processing a head reproduction signal obtained by simultaneously reading the magnetization data of two or more tracks of the recording medium simultaneously by the reproduction head;
The recording medium is arranged with the phase shifted by a length smaller than the recording magnetization length of 1 bit, which is equal to the shortest magnetization transition interval, along the moving direction of the recording magnetization bit of 1 bit of the adjacent track. Has a structure,
The data processing unit performs a process of decoding the data of the recording magnetization bit based on an addition signal obtained by simultaneously reading data of recording areas of two or more tracks of the recording medium by the reproducing head. A data storage device comprising a processing unit.   The data processing unit is based on two head reproduction signals obtained by the reproducing head while the reproducing head moves by at least one recording magnetization bit length in the head moving direction with respect to the recording medium. 2. The data storage apparatus according to claim 1, further comprising a processing unit that recursively decodes a subsequent signal using information obtained by decoding a preceding head reproduction signal.   The data processing unit includes a processing unit that performs a process of decoding data based on a head reproduction signal obtained by the reproducing head and a conversion table for converting the head reproduction signal into decoded data. Item 4. The data storage device according to Item 1.   Recording magnetization bits are recorded on the recording medium on a plurality of recording tracks so that the center of each bit is located at the magnetization transition point of the other track magnetization bit, and during reproduction, sampling is performed at the center of the magnetization bit of each track. Means for reading information, and the data processing unit appropriately equalizes the reproduction response by the reproduction head for the recording magnetization bits to the plurality of tracks so as to become a partial response channel, and the equalization The data storage device according to claim 1, further comprising: a processing unit that decodes data based on a maximum likelihood decoding method based on a signal from the device. A data storage method for a data storage device according to claim 1,
A data recording method for a data storage device, characterized in that binary data to be recorded on a recording medium of the data storage device is distributed to a plurality of tracks on the basis of a predetermined method and written to each track by a recording head. A data storage method for a data storage device according to claim 1,
The data processing unit decodes the data in the recording area based on the addition signal obtained by simultaneously reading out the data in the recording area of two or more tracks of the recording medium of the data storage device by the reproducing head. A data reproduction method for a data storage device, characterized by performing processing.

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